Gulf of Maine Warming Update: 2022 the Regions Second Warmest Year

Documenting one more year in a decade of above-average regional temperatures

Author

Adam Kemberling

Published

January 31, 2023

With an annual average sea surface temperature (SST) of 53.66°F — more than 3.72°F above normal — the Gulf of Maine experienced its 2nd warmest year on record in 2022. The region ranked in the top 3 warmest temperatures across all seasons, with the most extreme temperatures occurring in November.

Annual Sea Surface Temperatures

The annual average SST in the Gulf of Maine for 2022 was 53.66°F; this was 3.72°F above the long-term (i.e., 1982-2011) average. This year fell short of the previous warmest year on record — 2021 — 0.43°F. Since the early 1980s, the rate of warming in the Gulf of Maine 0.86°F / Decade has been more than triple that of the world’s oceans (0.27°F / Decade Figure 1).

Figure 1: A timeseries of annual average sea surface temperature anomalies for the Gulf of Maine (solid black line) from 1982 through r report_yr, illustrating that r report_yr was the 2nd warmest year on record. Long-term trendlines for the Gulf of Maine (blue) and the entire globe (green) show how much more quickly the Gulf of Maine is warming compared to the rest of the world.

The rate of warming in the region vary throughout the year. Comparisons across the four seasons (Figure 2) reveal that the Gulf of Maine is warming fastest during the July-September (nearly 4x the global ocean average), more than twice the rate seen during January-March (~3x the global ocean average).

Figure 2: Four timeseries panels of the annual averages for each season (solid black lines) for the Gulf of Maine. Decadal trends are overlaid to compare decadal trends in the Gulf of Maine (blue) and the entire globe (green). Rates are much faster in the Gulf of Maine across all seasons, with the smallest difference in rates during the spring.

There can be significant spatial variability in annually-averaged SST patterns. The Gulf of Maine in 2022 illustrated this fact with the region southeast of Georges Bank experiencing the highest SST anomalies (Figure 3). This area is more susceptible than other areas of the Gulf of Maine to large-scale variability in major oceanic currents, such as the relative influence of the Gulf Stream versus the Labrador Current.

Figure 3: Map of annual average sea surface temperature anomalies in 2021. The box outlined by the black dashed line denotes the region of study for the analysis presented throughout this report.

Looking at these spatial patterns in 3-month averages (Figure 4) shows just how “patchy” these pockets of above-average temperatures can be. During January-March, the areas to the south and southeast of the Gulf of Maine exhibit a strong mix of both above and below average surface temperature. During April-June, we can see that the water within the Gulf of Maine itself and the deeper waters just south of Georges Bank experienced warmer temperatures than the surrounding areas. In the second-half of the year, the exceptional warmth of the Gulf Stream is evident to the east and south of the area of study (dashed line), while the Gulf of Maine, itself, remains several degrees above the long-term average.

Figure 4: Maps of the 3-month averages in sea surface temperature anomalies in 2022.

When we compare the annual average SST for 2022 (53.66°F) to other unusually warm years in the Gulf of Maine, we see that it was ~0.4°F cooler than 2021, the warmest year on record(54.09°F). When we look at the deviation from the long-term average SST (i.e., the annual SST anomaly), the last decade stands out for its exceptional warmth (Figure 5). 2022 continues a pattern that began in 2010 of sustained above-average temperatures. With the exception of 2019 (ranked 13th), all of the last ten years remain in the top 10 for SST.

Figure 5: A ranking of the top 10 annual SST values [bars] and those years’ respective SST anomalies [x-axis].

Worldwide Temperatures

It was not just the Gulf of Maine that experienced exceptional warmth in 2022, however. Globally, 2022 was the 3rd warmest year for sea surface temperatures, and 6th-warmest for combined land & ocean temperatures..

Figure 6 shows annual average SST anomalies for oceans all over the world in 2022. While much of the Southern Ocean and expanses of the southeastern Pacific were anomalously cool (a feature of La Niña conditions), most of the world’s oceans experienced unusually warm temperatures in 2022. This is particularly true for northern mid-latitudes, especially the northwestern Pacific (off Japan) and along the eastern seaboard of the United States—a region that includes the Gulf of Maine.

Figure 6: Map of annual average sea surface temperature anomalies for the world’s oceans in 2022.

Daily Sea Surface Temperatures

The annual cycle of SST in the Gulf of Maine exhibits a familiar pattern with the lowest annual temperatures being observed in March, while the highest SSTs are observed in August (Figure 7). The average difference between the annual maximum SST in August and the annual minimum SST in March is 22.87 °F. In 2022, the difference between the maximum SST (Aug-07, 68.72°F) and minimum SST (Mar-19, 42.15°F) was 26.57 °F. Daily SST anomaly values never fell below +1.59 °F and reached as high as +7.36 °F above the long-term average.

A line chart shows the average sea surface temperature for each day of the year, and overlaid against it are notably smoother black lines representing the long-term mean, 10th percentile, and 90th percentile temperatures for those same days of the year. The area between the mean and the observed temperature is filled in with a solid color to indicate whether that day meets marine heatwave criteris. The observed temperatures for 2022 are above the 90th percentile for nearly the entire year, with the exception of two periods less than a week long in June and October.

Figure 7: A timeseries of marine heatwave (MHW) conditions in the Gulf of Maine extending from January 1 through December 301 2022. Black lines representing the long-term (i.e., 1982 – 2011) average SST, the 10th percentile (i.e., cold spell threshold), and 90th percentile (i.e., heatwave threshold) for a given day in the Gulf of Maine are labeled to indicate climatological reference points. A solid line (red for marine heatwave or blue for a non-heatwave day) indicate the observed SST for each day; red and blue shading illustrates whether each day is considered part of a MHW event.

Record Setting Daily Temperatures

?@fig-hottest-days shows the highest SST values ever recorded for each day of the year in the Gulf of Maine. Record-setting days that occurred in 2022 are denoted with dark red dots (?@fig-hottest-days). Indeed, daily high SST records were set for more than half of all days in November and December. The most daily records were set in November, which experienced record high SSTs for 24 of the month’s 30 days - or 80% of the month. In total, record high daily temperatures were reached on 169 days during2022; nearly 46% of days in 2022 experienced record high SSTs in the Gulf of Maine.

Figure 8: An illustration of the percentage of days during each month in 2022 when a record-high temperature was observed in the Gulf of Maine (e.g., 80% — 24 days — of November were new record-setting high temperatures).

More Persistent, Intense Heatwaves

A marine heatwave (MHW) is defined as a period when there are five or more consecutive days when the observed SST is greater than the 90th percentile of the long-term average for that day. Subsequent MHW periods that are separated by two or fewer daily average SSTs that fall below the threshold are still considered part of a MHW event. Figure 7 shows the long-term average SST (gray line labeled “Climatological Mean”), as well as the threshold for a MHW day (gray line labeled “Heatwave Threshold”). The solid line and shaded area in the figure shows the observed SST for that day and its distance from the climatological average; when it is red, the Gulf of Maine is experiencing MHW conditions.

The Gulf of Maine met the criteria for MHW status for 353 days in 2022. While the warmest temperatures of the year were experienced in August (as we would expect from the climatology for the region), the largest temperature anomalies were observed during the last days of November, when they breached 7 °F above the long-term average.

Comparing daily SST anomalies and MHW status for 2022 to the long-term record (Figure 9), as in the figure below — it becomes clear that the frequency, duration, and intensity of MHWs has not only increased in the past decade. In a world without human-caused climate change, we would expect, positive (warm) and negative (cool) SST anomalies to more or less balance out over the span of several years, as various patterns of natural climate variability alternate having a dominant influence in Earth’s climate (e.g., La Niña vs El Niño). What is being observed in the Gulf of Maine (and elsewhere around the world), however, is a loss of that balance: larger fractions of recent years are experiencing above average temperatures and cold spells are becoming vanishingly rare.

A figure displays the temperatures for each day of year as a colored stripe, organized with a row for each day such that the day of year aligns vertically. The lower two-thirds has a roughly equal balance between colors for warm (red) and cold (blue) temperature anomalies. The top third of the image is almost completely red as temperature anomalies rarely fall below the long-term average. Black dots are overlaid onto days that meet the criteria for a heatwave, they are rare in the lower section and common in the red section.

Figure 9: Heat map of daily SST anomalies from the beginning of 1982 through the end of 2022. Not only do more large warm anomalies (darker reds) appear more frequently in recent years, but the frequency and duration of marine heatwave events (black lines) in the Gulf of Maine has become more pronounced in the past decade.

Warming Rate

GMRI research was the first to reveal that the Gulf of Maine has been warming faster than the vast majority of the world’s ocean. Figure 10 updates this historical analysis by including data for 2022. Indeed, the story has not changed: the Gulf of Maine is warming faster than ~96.6% of the world’s ocean. The reason why this is so important is because the rate of change can have profound consequences for the biology of individual species and for the integrated ecology of entire food webs.

Figure 10: Maps illustrating the rate of warming (from 1982 through 2022) displayed as their relative percentiles for [left] the northwest Atlantic Ocean and [right] entire global ocean surface.

Concluding Thoughts:

In recent years, SSTs in the Gulf of Maine (and adjacent waters) have increased significantly and the rate of warming has accelerated. Combined, these climate-related impacts are beginning to have profound consequences for the marine ecology in the Gulf of Maine, with implications for the people and communities who rely on marine resources for their livelihoods and well-being. Research suggests there are two major factors driving these trends, one oceanographic and one atmospheric:

  1. Oceanographic: The Gulf of Maine is influenced by two primary oceanic currents: the Labrador Current and the Gulf Stream. Historically, there was a stronger influence of the Labrador Current on the water in the Gulf of Maine. That stronger flow helped keep the heat transported northward along the U.S. East Coast by the Gulf Stream further out to sea. More recently, scientists have observed changes occurring in the interplay between the Labrador Current and Gulf Stream. More Arctic-origin freshwater from melting sea ice and land-based ice is constricting the southward flow of the Labrador Current. This is allowing the Gulf Stream—which transports warm water from lower latitudes to spread out more at latitudes around the Gulf of Maine. This, in turn, allows warmer water, more heavily influenced by the Gulf Stream to “spill over” into the Gulf of Maine.

  2. Atmospheric: The North Atlantic Oscillation (NAO)— a large-scale pattern of natural variability in the atmosphere — has been in a “positive phase” more frequently over the past 10-15 years, meaning a more zonal (i.e., west-to-east) atmospheric pattern has dominated in the region. The relative decrease in “waviness” of the jet stream inhibits more consistent intrusions of cooler, Arctic air into the region.

While the oceanographic driver of the observed SST change in the Gulf of Maine has clear links to human-caused climate change, more research is needed to ascertain whether the NAO is experiencing significant changes as a result of anthropogenic climate change. Regardless, the atmospheric and oceanic conditions of the past several years combine to reveal an unambiguous trend: The Gulf of Maine is experiencing unprecedented warmth—and is heating up at a rate that is faster than almost anywhere else in the world’s oceans.


A Note on Data Sources

  • NOAA High Resolution SST data provided by the NOAA/OAR/ESRL PSL, Boulder, Colorado, USA, from their Web site at https://psl.noaa.gov/data/gridded/data.noaa.oisst.v2.highres.html.

Recommended Citation:

Gulf of Maine Research Institute. 2022. Gulf of Maine Warming Update: 2022 . https://gmri.org/stories/warming-22


OLD ASSETS:

Temperature Anomaly Horizons

One way to think about the severity of these changes is to think about temperature horizons. A temperature horizon captures how long temperatures remain above certain thresholds. Each threshold is designated its own temperature, and in this way we can see how long within a year temperatures remained: 1 to 2 or as much as 4\(^oC\) above normal.

Horizon plot of all years and their temperature anomaly horizons

Figure 11: Temperature anomaly horizons for all years of available satellite data (1982-2022). Horizons display how long temperatures were above certain thresholds (horizon width) and are colored by the strength of these events.

Comparing the Gulf’s Two Hottest Years

If we pull the horizons of our two hottest years on record it makes it easier to contrast where either one experienced acute high temperature events, and where there were sustained periods of above average temperatures.

Early into 2022 it was apparent that the year was on-par with the previous title-holder for warmest year on record.

Single year horizon plots comparing 2021 and 2022

Figure 12: Two horizon plots compare the timing and duration of elevated temperatures in the two warmest years on record, 2021 and now 2022. The width of a color horizon indicates the duration that temperatures were above that threshold.

The Balance of Hot and Cold

Another way to visualize the climate transition that we are observing is by looking at the fraction of each year spent in different temperature ranges. Under a steady climate we would expect over the long-term to spend similar amounts of the year experiencing relatively warm & cold temperatures. These periods would balance themselves out and we would on-average have experienced something similar to the long-term climate.

What we have been seeing in the Gulf of Maine recently has lost that sense of balance. Larger fractions of the year are shared by above average temperatures & cold spell events are becoming vanishingly rare.

Streamplot tracking fraction of each year spent in varying degrees of temperature anomalies

Figure 13: A streamplot shows the fraction of each year on record that temperature anomalies fell within ranges further from the climate reference period average. Since 2010 the Gulf of Maine’s temperatures shifted rapidly outside of this expected range and a large fraction of the year is now 2 degrees or more above that average (red).

 

A work by Adam A. Kemberling

Akemberling@gmri.org